Piezoelectric substance, piezoelectric element, liquid discharge head using piezoelectric element, and liquid discharge apparatus

ABSTRACT

A piezoelectric material, characterized in that a main component of the piezoelectric substance is PZT, which has perovskite type structure expressed in Pb(Zr x Ti 1-x )O 3  (x expresses an element ratio Zr/(Zr+Ti) of Zr and Ti in the formula), an element ratio Pb/(Zr+Ti) of Pb, Zr and Ti of the piezoelectric substance is 1.05 or more, and an element ratio Zr/(Zr+Ti) of Zr and Ti is 0.5 to 0.8 inclusive, and the piezoelectric substance has at least a perovskite type structure of monoclinic system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric substance, apiezoelectric element, a liquid discharge head using the same, and aliquid discharge apparatus.

2. Description of the Related Art

In recent years, a piezoelectric actuator has been paid attention to ata point that miniaturization and high densification of a motor ispossible, in a portable information device field, chemistry, and amedical field as a new motor which replaces an electromagnetic motor.The piezoelectric actuator does not generate an electromagnetic noise onthe occasion of its drive, and, is not influenced by noise. Furthermore,the piezoelectric actuator attracts attention as technology of makingsuch equipment with millimeter class size that is represented by amicromachine, and a minute piezoelectric element is requested as itsdrive source.

As for a piezoelectric element, generally, it is common to finely formand produce a sintered compact of a bulk material or a single crystalmember, which is given heat-treatment to a piezoelectric substance, indesired size and thickness with technology such as machining andpolishing. In addition, when forming a minute piezoelectric element, amethod of directly forming a piezoelectric element by coating andsintering a green sheet-like piezoelectric substance by using methods,such as a printing method, in a predetermined position on a substrate,such as metal or silicon is common. A thickness of such a compact from agreen sheet is tens to hundreds of micrometers, electrodes are providedin upper and lower sides of the piezoelectric substance, and a voltageis applied through the electrodes.

Heretofore, a small piezoelectric element which was used for a liquiddischarge head was produced by finely forming a piezoelectric substancein a bulk material with technology such as machining or polishing asmentioned above, or using a green sheet-like piezoelectric substance. Asa device using such a piezoelectric element, for example, there is aliquid discharge head which has unimorph type piezoelectric elementstructure. The liquid discharge head is equipped with a pressure chambercommunicating with an ink feed chamber, and an ink ejection orificecommunicating with the pressure chamber, and a vibrating plate withwhich the piezoelectric element is bonded or in which it is formeddirectly is provided and constructed in the pressure chamber. In suchconstruction, an ink droplet is discharged from the ink discharge portby compressing the ink in the pressure chamber by generating deflectionvibration, which is caused by expanding and contracting thepiezoelectric element by applying a predetermined voltage to thepiezoelectric element.

Although color ink jet printers have spread presently by using such anoperation, enhancement in their printing performance, and in particular,higher resolution, and high speed printing are requested. Therefore, ithas been attempted to attain high resolution and high speed printingusing multi-nozzle head structure in which a liquid discharge head hasbeen miniaturized. In order to miniaturize a liquid discharge head, itis necessary to miniaturize further a piezoelectric element fordischarging ink. Furthermore, recently, attempts of applying liquiddischarge heads to industrial applications such as straight-writing ofwiring have been also active. At that time, it is necessary to patternliquid with more various characteristics at higher resolution, andhence, further high performance of a liquid discharge head is requested.

In recent years, because of development of micromachine technology,researches of developing a highly precise micro piezoelectric element byforming a piezoelectric substance as a thin film, and using fineprocessing technology having been used in semiconductors have beenperformed. In particular, a thickness of a piezoelectric substanceformed by film methods, such as a sputtering method, a chemical vapordeposition method, a sol gel method, and a gas deposition method isgenerally hundreds of nanometers to tens of micrometers in the case ofan application to a piezoelectric actuator. Electrodes are provided onthe piezoelectric substance and a voltage is applied through theelectrodes.

On the other hand, research of high performance piezoelectric materials,having greater piezoelectric property, in connection withminiaturization of a piezoelectric element is also active. As apiezoelectric material which has attracted attention recently, there isa ferroelectric material which has the perovskite type structure whichis constructed in a general formula ABO₃. This material exerts excellentferroelectricity, pyroelectricity, and piezoelectricity as represented,for example, by Pb(Zr_(x)Ti_(1-x))O₃ (lead zirconate titanate: PZT).

When a piezoelectric element made of PZT is generally formed by a filmmethod, such as a sputtering method, a chemical vapor deposition method,a sol gel method, or a gas deposition method, a thin film obtained takesthe perovskite type structure which is constructed in the generalformula ABO₃. When the element ratio Pb/(Zr+Ti) of Pb, Zr and Ti isequal to or less than 1, which is a stoichiometric ratio of theperovskite type structure which is constructed in the general formulaABO₃, piezoelectricity drops rapidly. For this reason, when forming thepiezoelectric element made of PZT, Pb may be added a little moreexcessively than the stoichiometric ratio, and in particular, thesputtering method has that tendency remarkably. Nevertheless, when Pb isadded further in excess of the stoichiometric ratio, generally a leakagecurrent at the time of voltage application increases. For this reason,it was necessary to decide an optimum Pb excessive dosage with an effectof increase of leakage current, and piezoelectricity as trade-offrelation. (Non-Patent Document 1: FUJITSU.53, 2, p. 105-109 (March,2002)).

The present invention aims at providing a piezoelectric substance whichsolves the above-mentioned problems, has large piezoelectricity, anduses PZT, which can suppress a leakage current at the time of voltageapplication which becomes a problem at the time of lead excessiveaddition, as a main component, and a piezoelectric element using this.In addition, the present invention aims at providing a liquid dischargehead, which exerts uniform and high discharging performance and canperform fine patterning, and a liquid discharge apparatus having this.

SUMMARY OF THE INVENTION

The above-mentioned objects are achieved by a piezoelectric substance,characterized in that a main component of the piezoelectric substance isPZT, which has a perovskite type structure expressed inPb(Zr_(x)Ti_(1-x))O₃ (x expresses an element ratio Zr/(Zr+Ti) of Zr andTi in the formula), an element ratio Pb/(Zr+Ti) of Pb, Zr and Ti of thepiezoelectric substance is 1.05 or more, and an element ratio Zr/(Zr+Ti)of Zr and Ti is 0.5 to 0.8 inclusive, and the piezoelectric substancehas at least a perovskite type structure of a monoclinic system.

The present invention can provide a piezoelectric substance which haslarge piezoelectricity, and uses PZT, which can suppress a leakagecurrent at the time of voltage application which becomes a problem atthe time of lead excessive addition, as a main component, and apiezoelectric element using this.

Furthermore, using the above-mentioned piezoelectric element makes itpossible to obtain a liquid discharge head, which exerts uniform andhigh discharging performance and can perform fine patterning, and aliquid discharge apparatus having this.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a phase diagram of bulk PZT.

FIG. 2 is a diagram showing a change of a lattice constant by a changeof an element ratio of Zr and Ti of bulk PZT.

FIG. 3 is a schematic diagram of an example of a uniaxial crystal inthis embodiment, and a schematic dot diagram of positive electrode byX-ray diffraction thereof.

FIG. 4 is a schematic diagram of an example of a single crystal in thisembodiment, and a schematic positive peak diagram by X-ray diffractionthereof.

FIG. 5 is a schematic diagram showing an example of an embodiment of apiezoelectric element of this embodiment.

FIG. 6 is a schematic diagram showing an example of an embodiment of aliquid discharge head of this embodiment.

FIG. 7 is a sectional schematic diagram in a width direction of theliquid discharge head of FIG. 6.

FIG. 8 is a schematic diagram of the liquid discharge head of FIG. 6 inview of a top face side (discharge port side).

FIG. 9 is a schematic diagram of the liquid discharge head of FIG. 6 inview of a top face side (discharge port side).

FIG. 10 is a schematic diagram showing an example of a productionprocess of a liquid discharge head of this embodiment.

FIG. 11 is a schematic diagram showing another example of a productionprocess of a liquid discharge head of this embodiment.

FIG. 12 is a schematic diagram showing a further example of a productionprocess of a liquid discharge head of this embodiment.

FIGS. 13A, 13B, 13C, 13D, 13E and 13F are schematic diagrams showing anexample of a production process of a liquid discharge head of thisembodiment.

FIG. 14 is a perspective view showing an embodiment of a liquiddischarge apparatus of this embodiment.

FIG. 15 is a perspective view showing an embodiment of a liquiddischarge apparatus of this embodiment.

FIG. 16 includes reciprocal lattice mapping charts of {004} and {204} byX-ray diffraction of the piezoelectric substance in a first example.

DESCRIPTION OF THE EMBODIMENTS

The following description is with regards to a mechanism that uses thepiezoelectric element (piezoelectric thin film element) of the presentinvention and can achieve excellent features.

At the time of forming a PZT piezoelectric substance by a film method orheat sintering after forming a PZT piezoelectric substance, an A sitedefect of the perovskite type structure which is constructed in ABO₃,i.e., a defect of Pb arises, which becomes a major factor whichsignificantly obstructs piezoelectricity. Generally, for example, when aPZT piezoelectric substance is formed by the film methods such as asputtering method, an element ratio Pb/(Zr+Ti) of Pb, Zr and Ti of thepiezoelectric substance obtained becomes more than 1 which is astoichiometric ratio of the perovskite type structure which isconstructed in the general formula ABO₃. This is conceivable that Pb inexcess of the stoichiometric ratio is needed in order to make thisdefect not occur. Nevertheless, in this case, since Pb is not altogethertaken into A sites originally even if Pb is added considerablyexcessively, excessive Pb which is not taken into the A sites in thepiezoelectric substance acts as leakage sites. Hence, a leakage currentis increased.

FIG. 1 is a phase diagram of bulk PZT which is cited and shown from thedocument of Isaku Jinno, “Formation of Pb-based ferroelectric thin filmby ion beam sputtering method and research on its functional deviceapplication”, Osaka University Engineering Theory No. 13557, Feb. 25,1998, p. 35, FIG. 3-1(a).

A piezoelectric substance in a bulk in this specification points to aproduct by a sintering method or a pressure sintering method which isgenerally used as a production method of ceramics. In addition, apiezoelectric substance which is obtained using a green sheet which issintered after heat removal of a binder is also regarded as a bulk bodyin a wide sense.

As shown in FIG. 1, PZT having the perovskite type structure which isconstructed in ABO₃ has a crystal structure of a tetragonal (region“F_(T)”) when Zr/(Zr+Ti) according to the element ratio of Zr and Ti isless than 0.53 at a room temperature in the case of a bulk phase. Inaddition, PZT has a crystal structure of a rhombohedral (region“F_(R)(LT)”) and “F_(R)(HT)”) when Zr/(Zr+Ti) is 0.53 or more.Nevertheless, in the case that a piezoelectric substance has at leastthe perovskite type structure of a monoclinic system when the elementratio Zr/(Zr+Ti) of Zr and Ti is 0.5 to 0.8 inclusive, the followingphenomenon is conceivable. That is, even if the element ratio Pb/(Zr+Ti)of Pb, Zr, and Ti of the piezoelectric substance is 1.05 or more,excessive Pb does not act as leakage sites, and a leakage current doesnot increase. Hence, it becomes possible to make Pb contained moreexcessively. Consequently, A site defects of Pb decrease further andpiezoelectricity improves, and so on, for example.

Further, PZT having the perovskite type structure which is constructedin ABO₃ has a Curie temperature Tc₀ of 230° C. to 490° C. by the elementratio of Zr and Ti in bulk. However, in the case where the element ratioZr/(Zr+Ti) of Zr and Ti is 0.5 to 0.8 inclusive, the piezoelectricsubstance has at least a perovskite type structure of a monoclinicsystem and a Curie temperature Tc of the piezoelectric substance and aCurie temperature Tc₀ in bulk at the element ratio of Zr and Ti of thepiezoelectric substance satisfy the relation of Tc>Tc0+50° C., and thefollowing phenomenon is conceivable. That is, even if the element ratioPb/(Zr+Ti) of Pb, Zr and Ti of the piezoelectric substance is 1.05 ormore, excessive Pb does not act as leakage sites, and a leakage currentdoes not increase. Hence, it becomes possible to make Pb contained moreexcessively. Consequently, A site defects of Pb decrease further andpiezoelectricity improves, and so on, for example. Increase of Tc of thepiezoelectric substance of the present application embodiment is in astate that this excessive Pb does not act as leakage sites.

Embodiments of the present invention are described with reference to thedrawings.

FIG. 5 shows a schematic sectional drawing of an example of anembodiment of a piezoelectric element of the present invention. Apiezoelectric element 10 of the present invention is a piezoelectricelement including at least a first electrode film 6, a piezoelectricsubstance 7 which relates to the present invention, and a secondelectrode film 8. In the piezoelectric element of the embodiment shownin FIG. 5, although a sectional shape of the piezoelectric element 10 isin a rectangle, it may be also a trapezoid or an inverted trapezoid.Although the piezoelectric element 10 of the present applicationembodiment is formed on a substrate 5, a first electrode film 6 and asecond electrode film 8, which construct the piezoelectric element 10 ofthe present application embodiment may be a lower electrode and an upperelectrode respectively, and vice versa. This reason is based on aproduction method at the time of making the device, and either canobtain the effect of the present invention. In addition, there may be abuffer layer 9 between the substrate 5 and first electrode film 6.

It is possible to produce the piezoelectric element 10 of the presentapplication embodiment by forming the first electrode film 6 on at leastthe substrate 5 or the buffer layer 9 formed on the substrate 5, nextforming the piezoelectric substance 7 thereon, and further forming thesecond electrode 8.

A main component of the piezoelectric substance 7 of the presentapplication embodiment is lead zirconate titanate (PZT) which has aperovskite type structure expressed in Pb(Zr_(x)Ti_(1-x))O₃ (x denotesthe element ratio Zr/(Zr+Ti) of Zr and Ti in the formula). The elementratio Pb/(Zr+Ti) of Pb, Zr and Ti is 1.05 or more which is larger than1, which is the stoichiometric ratio of the perovskite type structure.Further, the element ratio Zr/(Zr+Ti) of Zr and Ti is 0.5 to 0.8inclusive. In addition, the piezoelectric substance 7 has at least aperovskite type structure of a monoclinic system.

The reason why the element ratio Pb/(Zr+Ti) of Pb, Zr and Ti is made1.05 or more is because piezoelectricity drops when Pb/(Zr+Ti)approaches 1 which is the stoichiometric ratio, and in particular,piezoelectricity drops rapidly when Pb/(Zr+Ti) is 1 or less. When Pb isadded further in excess of the stoichiometric ratio, generally a leakagecurrent at the time of voltage application increases. Although there isa tendency that its effect becomes remarkable in particular whenPb/(Zr+Ti) is 1.2 or more especially, a leakage current is suppressedeven if the piezoelectric substance 7 of the piezoelectric element 10 ofthe present application embodiment is made further excessive.Nevertheless, since it becomes difficult to produce a piezoelectricsubstance which has the perovskite type structure when it becomes tooexcessive, it is preferable to make Pb/(Zr+Ti) about 1.5 or less,usually.

In addition, a piezoelectric substance in bulk whose main component isPZT, which has the perovskite type structure which is constructed in thegeneral formula ABO₃, generally has crystal systems which are differentdepending on a temperature and the element ratio of Zr and Ti, as shownin FIG. 1. For example, as shown in FIG. 1, the piezoelectric substancebecomes respective crystal phases of a cubic (region “P_(c)”), atetragonal (region “F_(T)”), a rhombohedral (region “F_(R)(HT)” and“F_(R)(LT)”), and an orthorhombic (region “A_(T)”). In addition to this,a crystal phase of the piezoelectric substance 7 of this embodiment is amonoclinic. Here, the monoclinic in this embodiment means a crystalphase whose lattice constants of a unit lattice are β≠90°, α=γ=90°.Although α=β or α≠β is also sufficient, generally α and β are nearvalues. In addition, for example, although a plurality of crystalphases, such as a monoclinic and a tetragonal, a monoclinic and arhombohedral, a monoclinic and a tetragonal and a rhombohedral, andother crystal phases, may be intermingled, a monoclinic or a mixed phaseof a monoclinic and a crystal phase except a monoclinic is preferable.The element ratio Zr/(Zr+Ti) of Zr and Ti of the piezoelectric substance7 of this embodiment is 0.5 to 0.8 inclusive, and this is because it isdifficult to obtain a monoclinic when the element ratio Zr/(Zr+Ti) isless than 0.5, and it is difficult to produce a film which has theperovskite type structure when exceeding 0.8.

In addition, a PZT piezoelectric substance having the perovskite typestructure which is constructed in the general formula ABO₃ has a Curietemperature Tc₀ of 230° C. to 490° C. by the element ratio of Zr and Tigenerally in bulk as shown by the curve ABC in FIG. 1. In the presentembodiment, the Curie temperature means a critical temperature at whichpolarization disappears. Generally, many perovskite type ferroelectriccrystals have crystal structure that is a tetragonal at a hightemperature and cubic at room temperature (rhombohedral or orthorhombicin the case of PZT). Although a perovskite type ferroelectric crystaldoes not have spontaneous polarization at a high temperature since it iscubic, when a temperature falls, it becomes tetragonal, rhombohedral, ororthorhombic through a phase transition point for spontaneouspolarization to occur. This temperature at which phase transition occursis called the Curie temperature. In a Curie temperature survey of apiezoelectric substance, generally, a temperature at which a dielectricconstant shows the maximum near a phase transition point, when atemperature is raised or lowered gradually, is made a Curie temperature.The Curie temperature Tc of the piezoelectric substance of thisembodiment was also measured by such a method. When the piezoelectricsubstance of this embodiment is made the same element ratio as that inbulk, the Curie temperature Tc preferably satisfies the relation ofTc>Tc₀+50° C. In particular, when Tc of the piezoelectric substancesatisfies the above-described relation, the element ratio Zr/(Zr+Ti) ofZr and Ti is preferably 0.2 to 0.8 inclusive. This is becausepiezoelectricity of the film falls when the element ratio Zr/(Zr+Ti) ofZr and Ti is less than 0.2, and it is difficult to produce apiezoelectric substance which has the perovskite type structure whenexceeding 0.8. Here, the Curie temperature Tc of the piezoelectricsubstance of this embodiment is a temperature at which a dielectricconstant at 1 kHz of the piezoelectric substance shows the maximum.

Further, it is particularly preferable that the piezoelectric substanceof this embodiment is a monoclinic or a mixed phase of a monoclinic andanother crystal phase, the relation of Tc>Tc₀+50° C. is satisfied, andthe element ratio Zr/(Zr+Ti) of Zr and Ti is 0.5 to 0.8 inclusive. Stillfurther, it is more preferable that the element ratio Zr/(Zr+Ti) of Zrand Ti is 0.5 to 0.6 inclusive. This is because piezoelectricity of sucha piezoelectric substance is the highest and a leakage current does notincrease in spite of excessive addition of Pb, and hence, while becomingpossible to apply a large voltage to the piezoelectric substance, it ispossible to obtain a long-life piezoelectric substance.

In addition, the piezoelectric substance of this embodiment may be whatis formed from a composition produced by doping a trace amount ofelement in the above-mentioned main components. For example, it may be apiezoelectric substance formed from something like La-doped PZT:PLZT[(Pb, La)(Z, Ti)O₃].

Furthermore, as for a film thickness of the piezoelectric substance ofthe present invention, it is preferable to be 1 μm to 10 μm inclusive.When a film thickness of the piezoelectric substance is made 1 μm ormore, it is possible to obtain the piezoelectric substance with amonoclinic phase easily. In addition, when being made 10 μm or less, itis possible to form the piezoelectric substance easily by a film methodsuch as a sputtering method.

Moreover, it is preferable that lattice parameters a and c of thepiezoelectric substance of this embodiment satisfy the relation of1.005<c/a<1.05. FIG. 2 is a diagram which is cited and shown from thedocument of Isaku Jinno, “Formation of Pb-based ferroelectric thin filmby ion beam sputtering method and research on its functional deviceapplication”, Osaka University Engineering Theory No. 13557, Feb. 25,1998, p. 35, FIG. 3-1(b). As shown in FIG. 2, as for a PZT piezoelectricsubstance having the perovskite type structure which is constructed inthe general formula ABO₃ in a bulk, generally, its lattice constantschange according to the element ratio Zr/(Zr+Ti) of Zr and Ti. Inaddition, it is preferable that the lattice parameters a and c of thepiezoelectric substance of this embodiment satisfy the relation of1.005<c/a<1.05, and it is more preferable that a lattice constant a anda lattice constant a₀ in the bulk in the element ratio of Zr and Tisatisfy the relation of a≧a₀. This is because, when satisfying theabove-mentioned relations, a leakage current of the piezoelectricsubstance is further suppressed. Although this detailed reason isunknown, it is conceivable that the A site defects of Pb mentioned abovefurther decrease, and this change appears in a change of the latticeconstants.

In addition, a case where the piezoelectric substance is constructedfrom a uniaxial crystal or a single crystal is preferable because thepiezoelectric substance has larger piezoelectricity, and hence, ispreferable. Similarly, a case of being <100> orientation is preferablebecause the piezoelectric substance has further larger piezoelectricity.At this time, higher <100> orientation of the piezoelectric substance ismore preferable, and the case where the piezoelectric substance isconstructed from a single crystal and an orientation rate is 100% ismost preferable.

Here, the orientation in the present invention means having singlecrystal orientation in a thickness direction. For example, <100>orientation is that crystal axes in a thickness direction of thepiezoelectric substance are aligned in the <100> direction. It ispossible to confirm using X-ray diffraction whether the piezoelectricsubstance of this embodiment has the orientation. For example, anexample of the piezoelectric substance with the <100> orientation whichis constructed of a piezoelectric substance whose main component is PZTwith the perovskite type structure will be shown below. As to peaksresulting from a piezoelectric substance measured by 2θ/θ measurement ofX-ray diffraction, only peaks belonging to an {L00} plane (L=1, 2, 3 . .. , n: n is an integer), such as {100} and {200} are detected. Inaddition, {100} in the present invention is an expression of genericallynaming a total of six planes generally expressed in (100), (010), (001),and the like. Similarly, <100> in the present invention is an expressionof generically naming a total of six orientations generally expressed in[100], [010], [001], and the like.

Generally, for example, [100] and [001] are the same when a crystalsystem is a cubic, but they should be distinguished in the case of amonoclinic, a tetragonal, or a rhombohedral. However, even if beingmonoclinic, tetragonal, or rhombohedral, a crystal with the perovskitetype structure which is represented by PZT has lattice constants nearthose of a cubic. Hence, in the present invention, [100] and [001] of atetragonal, and [111] and [-1-1-1] of a rhombohedral are namedgenerically <100> and <111>. In addition, although <100> orientation inthe present invention means that the piezoelectric substance has <100>single crystal orientation in a thickness direction, it is called the<100> orientation even if a crystal axis has a tilt of several degrees,for example, a <100> crystal axis leans by about 5° from the thicknessdirection.

It is possible to confirm an orientation rate of the piezoelectricsubstance of this embodiment using X-ray diffraction. For example, whena piezoelectric substance is <100> orientation, the piezoelectricsubstance is arranged so that diffraction of {100} of the piezoelectricsubstance may be most strongly detected by 2θ/θ measurement of X-raydiffraction. At this time, the <100> orientation rate is defined as arate of the sum of all the reflection peak strengths resulting from an{L00} plane (L=1, 2, 3 . . . , n: n is an integer) to the sum of all thereflection peak strengths resulting from piezoelectric substance.

In addition, although a uniaxial crystal in the present invention meansa crystal having single crystal orientation in a thickness direction ofa piezoelectric substance, intra-film orientation of a crystal is noobject especially. For example, a<100> uniaxial crystal is a film that acrystal with only <100> orientation is formed in its thicknessdirection. It is possible to confirm using X-ray diffraction whether thepiezoelectric substance of this embodiment is the uniaxial crystal. Forexample, in the case of a piezoelectric substance which is constructedof <100> uniaxial crystals of PZT with the perovskite type structure, asto peaks resulting from the piezoelectric substance in the 2θ/θmeasurement of X-ray diffraction, only peaks of an {L00} plane (L=1, 2,3 . . . , n: n is an integer), such as {100} and {200} are detected. Inaddition, when pole measurement of a {110} asymmetric plane isperformed, poles of the {110} asymmetric planes of respective crystalsare measured as a ring-like pattern in positions where an inclination ofthe piezoelectric substance from the thickness direction (normal linedirection of {L00} planes of crystals of the piezoelectric substance)shown by an arrow in FIG. 3 corresponds to about 45°.

In addition, the single crystal in the present invention means a crystalhaving single crystal orientation in a film thickness direction and anintra-film direction. For example, a piezoelectric substance which isconstructed of a <100> single crystal is a piezoelectric substanceconstructed of a single crystal or a plurality of crystals whosethickness direction is only <100> orientation, and in which a certaindirection in an intra-film direction is only <110> orientation. It ispossible to confirm using X-ray diffraction whether the piezoelectricsubstance of this embodiment is the uniaxial crystal. For example, inthe case of a piezoelectric substance which is constructed of a <100>single crystal of PZT with the perovskite type structure, as to peaksresulting from the piezoelectric substance in the 2θ/θ measurement ofX-ray diffraction, only peaks of an {L00} plane (L=1, 2, 3 . . . , n: nis an integer), such as {100} and {200} are detected. In addition, whenpole measurement of a {110} asymmetric plane is performed, a patternshown in FIG. 4 is measured. That is, poles of the {110} asymmetricplanes of respective crystals are measured as a fourfold-symmetricspot-like pattern in positions every 90° on a circumference where aninclination of the piezoelectric substance from the thickness direction(normal line direction of (L00) planes of crystals of the piezoelectricsubstance) shown by an arrow corresponds to about 45°.

In addition, as for the single crystal or uniaxial crystal in thisembodiment, the following is mentioned. For example, the polemeasurement of {110} asymmetric planes is performed using the PZTperovskite type structure with <100> orientation. At this time, acrystal poles of the {110} asymmetric planes of respective crystals aremeasured as an eightfold- or twelvefold-symmetric pattern in positionsevery 45° or 30° on a circumference where an inclination of thepiezoelectric substance from the thickness direction (normal linedirection of {L00} planes of crystals of the piezoelectric substance)corresponds to about 45° is mentioned. In addition, since a crystal apattern of which is not a spot but an elliptic is also a crystal whichhas intermediate symmetry between the single crystal and uniaxialcrystal in this embodiment, this is regarded as a single crystal or auniaxial crystal in a wide sense. Similarly, in the present embodiment,for example, also when a plurality of crystal phases such as amonoclinic and a tetragonal, a monoclinic and a rhombohedral, amonoclinic, a tetragonal, and a rhombohedral, a monoclinic and anothercrystal phase are intermingled (mixed phase), each of these is regardedas a single crystal or a uniaxial crystal in a wide sense. Furthermore,also when a crystal resulting from a twin crystal or the like isintermingled, or there is a dislocation, a defect, or the like, it isregarded as a single crystal or a uniaxial crystal in a wide sense.

Although crystal orientation of the piezoelectric substance of thisembodiment can be easily confirmed by the X-ray diffraction as mentionedabove, besides the above-described X-ray diffraction, for example, it ispossible to confirm it by sectional observation by a transmissionelectron microscope (TEM) or the like. In this case, also in the casewhere crystal dislocation exists columnarly in a thickness direction ora twin crystal can be confirmed, it is regarded as a single crystal in awide sense.

It is possible to specify a crystal phase of a piezoelectric substanceby reciprocal space mapping of the X-ray diffraction. For example, whena piezoelectric substance with <100> orientation of PZT is a cubic,reciprocal lattice points of (004) and (204) are measured by thereciprocal space mapping. Consequently, relation between magnitudeQ_(y)(004) in the y-axis direction of a (004) reciprocal lattice pointand magnitude Q_(y)(204) in the y-axis direction of a (204) reciprocallattice point becomes Q_(y)(004)=Q_(y)(204). Hence, it is possible toobtain such reciprocal lattice points that the relation between themagnitude Q_(y)(004) in the y-axis direction of a (004) reciprocallattice point and the magnitude Q_(x)(204) in the x-axis direction of a(204) reciprocal lattice point may become Q_(y)(004)=2Q_(x)(204).

In addition, when a piezoelectric substance with <100> orientation ofPZT is a tetragonal, reciprocal lattice points of (004) and (204) aremeasured by the reciprocal space mapping. Consequently, relation betweenmagnitude Q_(y)(004) in the y-axis direction of a (004) reciprocallattice point and magnitude Q_(y)(204) in the y-axis direction of a(204) reciprocal lattice point becomes Q_(y)(004)=Q_(y)(204). Hence, itis possible to obtain such reciprocal lattice points that the relationbetween the magnitude Q_(y)(004) in the y-axis direction of a (004)reciprocal lattice point and the magnitude Q_(x)(204) in the x-axisdirection of a (204) reciprocal lattice point may becomeQ_(y)(004)<2Q_(x)(204).

In addition, when a piezoelectric substance with <100> orientation ofPZT is a monoclinic, (004) and (204) are measured by the reciprocalspace mapping. Consequently, relation between magnitude Q_(y)(004) inthe y-axis direction of a (004) reciprocal lattice point and magnitudeQ_(y)(204) in the y-axis direction of a (204) reciprocal lattice pointbecomes Q_(y)(004)>Q_(y)(204) or Q_(y)(004)<Q_(y)(204). Hence, it ispossible to obtain such reciprocal lattice points that the relationbetween the magnitude Q_(y)(004) in the y-axis direction of the (004)reciprocal lattice point and the magnitude Q_(x)(204) in the x-axisdirection of the (204) reciprocal lattice point may becomeQ_(y)(004)<2Q_(x)(204). At this time, it is no matter even if two (204)reciprocal lattice points which become Q_(y)(004)>Q_(y)(204) andQ_(y)(004)<Q_(y)(204) appear. It seems that these two reciprocallattices have relation of a twin crystal.

In addition, when a piezoelectric substance with <100> orientation ofPZT is a rhombohedral, (004) and (204) are measured by the reciprocalspace mapping. Consequently, relation between magnitude Q_(y)(004) inthe y-axis direction of a (004) reciprocal lattice point and magnitudeQ_(y)(204) in the y-axis direction of a (204) reciprocal lattice pointbecomes Q_(y)(004)>Q_(y)(204) or Q_(y)(004)<Q_(y)(204). Hence, it ispossible to obtain such reciprocal lattice points that the relationbetween the magnitude Q_(y)(004) in the y-axis direction of the (004)reciprocal lattice point and the magnitude Q_(x)(204) in the x-axisdirection of (204) may become Q_(y)(004)≈2Q_(x)(204). At this time, itis no matter even if two (204) reciprocal lattice points which becomeQ_(y)(004)>Q_(y)(204) and Q_(y)(004)<Q_(y)(204) appear. It seems thatthese two reciprocal lattices have relation of a twin crystal.

Similarly, also in another orientation or another crystal phase, it ispossible to specify simply a crystal phase of a piezoelectric substanceby the reciprocal space mapping of the X-ray diffraction. Besides theabove-described method, it is possible to perform confirmation also by,for example, sectional observation by a TEM or the like. Here, they-axis of a reciprocal space is a thickness direction of a piezoelectricsubstance, and the x-axis is a certain direction in the intra-filmdirection of the piezoelectric substance.

Although a forming method of the piezoelectric substance of thisembodiment is not limited particularly, in regard to a thin film of 10μm or less, usually, it is possible to use thin film forming methodssuch as the sol gel method, a hydrothermal crystallization method, thegas deposition method, and an electrophoresis. Furthermore, it ispossible to use thin film forming methods such as the sputtering method,chemical vapor phase deposition method (CVD method), a metal-organicchemical vapor deposition (MOCVD method), an ion beam deposition method,a molecular beam epitaxy method, and a laser ablation method. Sincethese thin film forming methods make it possible to make a piezoelectricsubstance uniaxialized or single-crystallized by using epitaxial growthfrom a substrate or a lower electrode, it becomes easy to form thepiezoelectric element which has further higher piezoelectricity.

It is preferable to form the piezoelectric substance 7 of thisembodiment by the sputtering method. A target whose main component islead zirconate titanate is used as a target. It is preferable to makethe element ratio {Pb/(Zr+Ti)}Target of Pb, Zr and Ti of a targetPb/(Zr+Ti)>{Pb(Zr+Ti)} Target to the element ratio Pb/(Zr+Ti) of thepiezoelectric substance.

When the piezoelectric substance 7 is formed by the sputtering method sothat the above-mentioned relation may be satisfied, it is possible tosuppress an increase of a leakage current in spite of an excessiveaddition of Pb. In addition, it is preferable to use a target, whosemain component is lead zirconate titanate whose target density is 90% orless, as a target. Thereby, it is possible to easily form apiezoelectric substance that the element ratio Pb/(Zr+Ti) of Pb, Zr andTi of the piezoelectric material satisfies relation ofPb/(Zr+Ti)>{Pb/(Zr+Ti)}Target to the element ratio {Pb/(Zr+Ti)}Target ofPb, Zr and Ti of a target. In addition, the above-mentioned targetdensity (%) is a density (%) of a target to a theoretical density oflead zirconate titanate.

When a piezoelectric substance is formed in this manner, even if a filmthickness of the piezoelectric substance is 1 μm or more, it becomeseasy to obtain the piezoelectric substance with a monoclinic. Themonoclinic piezoelectric substance of this embodiment is a crystal phasewhich is particularly easy to obtain the element ratio Zr/(Zr+Ti) of Zrand Ti which is 0.5 to 0.6 inclusive. This composition is called acrystal phase boundary (Morphotropic Phase Boundary: MPB) composition ofbulk PZT, and it is especially possible to expect largepiezoelectricity.

As a forming method of a piezoelectric substance by the sputteringmethod, it is possible to mention a heat sputtering method of forming asubstrate at about 600° C. with heating it so as to obtain apiezoelectric substance a main component which is PZT which has theperovskite type structure. In addition, it is possible to mention alow-temperature sputtering method of making a piezoelectric substance aperovskite type crystal by post-sintering after forming thepiezoelectric substance, whose main component is amorphous PZT, at atemperature of 300° C. or less. In the forming method of thepiezoelectric substance in this embodiment, either method may be used.In addition, it is also sufficient to perform post-sintering afterforming a piezoelectric substance by the heat sputtering method.Nevertheless, since the heat sputtering method is easier foruniaxialization and single crystallization of a piezoelectric substance,it is preferable to form the piezoelectric substance using the heatsputtering method.

The piezoelectric element of this embodiment has the piezoelectricsubstance of this embodiment, and a pair of electrodes which contactsthe piezoelectric substance. It is preferable that a first electrode(electrode film) or a second electrode (electrode film) of thepiezoelectric element of this embodiment has satisfactory adhesion withthe above-mentioned piezoelectric substance, and is constructed of ahighly conductive material, that is, a material having a specificresistance of an upper electrode film or a lower electrode film of 10⁻⁷to 10⁻² ohm·cm. Although such a material is generally a metal in manycases, it is preferable to use a metal of a Pt group, such as Au, Ag,Cu, Ru, Rh, Pd, Os, Ir, or Pt, as an electrode material. In addition,since an alloy material which includes the above-mentioned material,such as silver paste or solder also has high electroconductivity, it ispossible to preferably use it. In addition, conductive oxide materials,such as IrO (oxidation iridium), SRO (ruthenium acid strontium), ITO(conductive tin oxide), and BPO (barium metaplumbate), are alsopreferable as electrode materials. In addition, either one-layerstructure or multilayer structure may be sufficient as the electrodefilm. For example, in order to increase adhesion with a substrate,structure such as Pt/Ti may be also sufficient. As to a film thicknessof the electrode film, it is preferable to be about 100 to 1000 nm, andit is further preferable to be 500 nm or less. When the film thicknessof the electrode film is made 100 nm or more, resistance of theelectrode film becomes small enough, and when 1000 nm or less, there isno possibility of obstructing the piezoelectricity of the piezoelectricelement, and hence, it is preferable.

In addition, when the first electrode film contains an oxide electrodefilm with the perovskite type structure which is given at least <100>orientation, it is possible to produce easily a uniaxial film or asingle crystal film which is given <100> orientation. In particular,since SRO has a lattice constant of about 4 Å close to a latticeconstant of PZT, it is possible to easily produce a uniaxial film or asingle crystal film.

Although a forming method of the electrode film in this embodiment isnot limited particularly, in regard to a thin film of 1000 nm or less,usually, it is possible to form it using thin film forming methods suchas the sol gel method, hydrothermal crystallization method, gasdeposition method, and electrophoresis. Furthermore, it is possible toform it using thin film forming methods such as the sputtering method,CVD method, MOCVD method, ion beam deposition method, molecular beamepitaxy method, and laser ablation method. Since these thin film formingmethods make it possible to make the electrode film uniaxialized orsingle-crystallized by using epitaxial growth from a substrate or abuffer layer, it becomes easy to make the piezoelectric substanceuniaxialized or single-crystallized.

Next, a liquid discharge head of this embodiment will be explained.

The liquid discharge head of this embodiment has a discharge port, anindividual liquid chamber communicating with the discharge port, apiezoelectric element provided in correspondence with the individualliquid chamber, and a vibrating plate provided between theabove-mentioned individual liquid chamber and the above-mentionedpiezoelectric element. Furthermore, the liquid discharge head ischaracterized in that liquid in the above-mentioned individual liquidchamber is discharged from the above-mentioned discharge port by avolume change in the above-mentioned individual liquid chamber occurringby the above-mentioned vibrating plate, and that the above-mentionedpiezoelectric element is the piezoelectric element of this embodiment.

Using the piezoelectric element of this embodiment as a piezoelectricelement makes it possible to easily obtain a liquid discharge head,which exerts uniform and high discharging performance and can performfine patterning. The liquid discharge head of this embodiment may beused for image forming apparatuses, such as a liquid dischargeapparatus, a fax, a compound machine, and a copier, or industrialdischarge apparatus of discharging liquid other than ink.

The liquid discharge head of this embodiment will be explained withreference to FIG. 6. FIG. 6 is a schematic diagram showing an example ofthe embodiment of the liquid discharge head of this embodiment. Theliquid discharge head of this embodiment shown in FIG. 6 is equippedwith a discharge port 11, a communication hole 12 which makes thedischarge port 11 and an individual liquid chamber 13 communicate witheach other, and a common liquid chamber 14 which supplies liquid to theindividual liquid chamber 13. And, the liquid is supplied to thedischarge port 11 along with this communication route. A part of theindividual liquid chamber 13 is constructed of a vibrating plate 15. Thepiezoelectric element 10 for giving vibration to the vibrating plate 15is provided in the exterior of the individual liquid chamber 13. Whenthe piezoelectric element 10 is driven, the vibrating plate 15 is givenvibration by the piezoelectric element 10, and causes a volume change inthe individual liquid chamber 13. Thereby, the liquid in the individualliquid chamber 13 is discharged from the discharge port. Although thepiezoelectric element 10 is rectangular in the embodiment shown in FIG.6, this shape may be also elliptical, circular, and parallelogramic.

FIG. 7 shows a sectional schematic diagram in a width direction of theliquid discharge head shown in FIG. 6. The piezoelectric element 10which constructs the liquid discharge head of this embodiment will beexplained further in detail with reference to FIG. 7. Although asectional shape of the piezoelectric element 10 is shown by as arectangle, a trapezoid or an inverted trapezoid may be also sufficient.In addition, although the first electrode film 6 is equivalent to thelower electrode film 16 and the second electrode film 8 is equivalent tothe upper electrode film 18 in FIG. 7, the first electrode film 6 andsecond electrode film 8 which construct the piezoelectric element 10 ofthis embodiment may be made the lower electrode film 16 and upperelectrode film 18, respectively, and vice versa. This is based on aproduction method at the time of device production, and either canobtain the effect of the present embodiment. In addition, the vibratingplate 15 may be formed from the substrate 5 which constructs thepiezoelectric element 10 of this embodiment. In addition, there may be abuffer layer 19 between the vibrating plate 15 and the lower electrodefilm 16.

FIGS. 8 and 9 are schematic diagrams of the liquid discharge head, shownin FIG. 6, in view of a top face side (discharge port 11 side). A region13 shown by a dotted line expresses the individual liquid chamber 13 towhich pressure is applied. The piezoelectric element 10 is patternedsuitably and formed on the individual liquid chamber 13. For example, inFIG. 8, the lower electrode film 16 is drawn out to a portion in whichthe piezoelectric substance 7 does not exist, and the upper electrodefilm 18 (not shown) is drawn out to an opposite side of the lowerelectrode film 16 and is connected to a drive source. Although FIGS. 8and 9 show a state that the lower electrode film 16 has been patterned,it may exist in a portion where the piezoelectric substance 7 does notexist as shown in FIG. 7. When there is no trouble, such as a short anddisconnection, between a drive circuit and the piezoelectric element 10when driving the piezoelectric element 10, the piezoelectric substance7, lower electrode film 16, and upper electrode film 18 can be optimallypatterned in accordance with an object. In addition, a reason why ashape of the individual liquid chamber 13 is shown in a parallelogram isbecause it becomes such a shape when an individual liquid chamber isproduced by wet etching by alkali using an Si (110) substrate as asubstrate. Besides this, the shape of the individual liquid chamber 13may be either a rectangle or a square. Generally, although two or moreindividual liquid chambers 13 are produced in fixed intervals on thevibrating plate 15, as shown in FIG. 9, the individual liquid chambers13 may be disposed in staggered arrangement, or the number of them maybe one depending on an object.

A thickness of the vibrating plate 15 is usually 0.5 to 10 μm, and is1.0 to 6.0 μm preferably. When there is the above-mentioned buffer layer19, the thickness of the buffer layer is also included in thisthickness. In addition, a plurality of layers besides the buffer layermay be formed. For example, when forming a vibrating plate and anindividual liquid chamber from the same substrate, a required etch stoplayer and the like may be included. A width Wa (refer to FIG. 8) of theindividual liquid chamber 13 is usually 30 to 180 μm. Although a lengthWb (refer to FIG. 8) is based also on an amount of discharge liquiddroplets, it is usually 0.3 to 6.0 mm. A form of the discharge port 11is usually a circular or a star, and a diameter is preferably 7 to 30 μmusually. It is preferable that a sectional shape of the discharge port11 is a tapered shape expanded in a direction of the communication hole12. A length of the communication hole 12 is usually 0.05 to 0.5 mmpreferably. When the length of the communication hole 12 is made 0.5 mmor less, discharging speed of a liquid droplet becomes fast enough. Inaddition, when being 0.05 mm or more, dispersion in the dischargingspeed of a liquid droplet which is discharged from each discharge portbecomes small preferably. In addition, members which form the vibratingplate, individual liquid chamber, common liquid chamber, communicationhole, and the like which construct the liquid discharge head of thisembodiment may be the same material, or may be different materials,respectively. For example, when it is Si and the like, it is processiblewith sufficient accuracy by using a lithography method and an etchingmethod. In addition, as members selected when different ones, materials,difference among coefficients of thermal expansion each of which is1×10⁻⁸/° C. to 1×10⁻⁶/° C., are preferable. For example, it ispreferable to select a SUS substrate, Ni substrate, and the like to a Sisubstrate.

Next, a production method of a liquid discharge head of this embodimentwill be explained. The production method of a liquid discharge head ofthis embodiment has at least the following steps.

(1) Step of forming discharge port

(2) Step of forming communication hole making discharge port andindividual liquid chamber communicate

(3) Step of forming individual liquid chamber

(4) Step of forming common liquid chamber communicating with individualliquid chamber

(5) Step of forming vibrating plate giving vibration to individualliquid chamber

(6) Step of producing piezoelectric element of this embodiment forgiving vibration to vibrating plate provided in exterior of individualliquid chamber

Specifically, for example, as a first method of producing the liquiddischarge head of this embodiment, a method to be described next can bementioned. First, a part of an individual liquid chamber and a vibratingplate are formed with applying step (3) on a substrate on which thepiezoelectric element 10 is formed with applying the above-mentionedstep (6). A substrate on which the communication hole and the commonliquid chamber are formed with applying steps (2) and (4) separately,and a substrate having the discharge port is produced with applying step(1). Next, the above-mentioned substrates and these substrates arestacked and unified, and the liquid discharge head is produced.

In addition, as a second method of producing the liquid discharge headof this embodiment, a method to be described next can be mentioned.First, separately, a substrate on which an individual liquid chamber isformed with applying at least step (3), or a substrate on which anindividual liquid chamber is formed is produced. Next, the piezoelectricelement, or the vibrating plate and piezoelectric element aretransferred on this from the substrate on which the piezoelectricelement is formed with applying step (6) or the substrate on which thevibrating plate and piezoelectric element are formed at steps (5) and(6). Next, the individual liquid chamber is formed by processing asubstrate portion in a side, which faces at least the piezoelectricelement and the like, of the substrate, on which the piezoelectricelement, or the vibrating plate and piezoelectric element aretransferred, with applying step (2). Further, similarly to theabove-described first method, the substrate on which the communicationhole and common liquid chamber are formed, and the substrate on whichthe discharge port is formed are produced, and these substrates arestacked and unified for the liquid discharge head to be produced.

As the first method, as shown in FIG. 10, first, similarly to theproduction method of a piezoelectric element, the piezoelectric element10 is provided on the substrate 5. Next, the vibrating plate 15 isformed while removing a part of the substrate 5 at least in a state ofpatterning the piezoelectric element 10 to form a part of the individualliquid chamber 13. Separately, a substrate which has the common liquidchamber 14 and communication hole 12 is produced, and further, asubstrate on which the discharge port 11 is formed is produced. It ispossible to mention a production method of further stacking and unifyingthese to form the liquid discharge head. As a method of removing a partof the substrate 5, it is possible to mention a method, such as a wetetching method, a dry etching method, or a sand mill method. It ispossible to form at least parts of the vibrating plate 15 and individualliquid chamber 13 by removing a part of the substrate 5 by such amethod.

As the second method, for example, as shown in FIG. 11, first, similarlyto the production method of a piezoelectric element, the piezoelectricelement 10 is provided on the substrate 5. Next, a substrate on whichthe vibrating plate 15 is formed as a film on the piezoelectric elementin a state that the piezoelectric element 10 is not patterned isproduced. It is possible to mention a production method of furtherproducing a substrate of providing the individual liquid chamber 13, asubstrate of providing the communication hole 12 and common liquidchamber 14, a substrate of providing the discharge port 11, and thelike, stacking these thereafter, and transferring the vibrating plate,piezoelectric element, and the like from the above-mentioned substrates.

Moreover, as shown in FIG. 12, first, the piezoelectric element 10 isformed on the substrate 5, and this is patterned for the piezoelectricelement to be formed. Separately, a substrate of providing the vibratingplate 15 on the substrate and further providing a part of the individualliquid chamber 13, a substrate of providing the common liquid chamber 14and communication hole 12, and a substrate of forming the discharge port11 are produced. It is possible to mention a production method offurther stacking these, and transferring the piezoelectric element 10 onthis from the above-mentioned substrate to form the liquid dischargehead.

As a bonding method at the time of transfer, although a method of usingan inorganic adhesive or an organic adhesive may be used, metal bondingby an inorganic material is more preferable. As a material used for themetal bonding, it is possible to mention In, Au, Cu, Ni, Pb, Ti, Cr, Pd,and the like. Since it is possible to perform bonding at a lowtemperature of 300° C. or less and difference of a coefficient ofthermal expansion therebetween that of the substrate becomes small whenthese are used, there is also little damage to the piezoelectric elementwhile it is possible to avoid a problem by warpage of the piezoelectricelement and the like when being elongated.

It is possible to form the communication hole 12 and common liquidchamber 14 in the first method, and the individual liquid chamber 13,communication hole 12, and common liquid chamber 14 in the second methodby performing, for example, a step of patterning a forming member(substrate) by lithography, and a step of removing a part of the memberby etching. For example, in the case of the second method, theindividual liquid chamber 13, communication hole 12, and common liquidchamber 14 are formed by steps a) to e) shown in FIGS. 13A, 13B, 13C,13D, 13E and 13F. FIG. 13A shows a forming step of a mask for theindividual liquid chamber 13, and FIG. 13B shows a step of processingthe individual liquid chamber 13 (a hatched portion means a processedportion) by etching and the like from an upper portion. In addition,FIG. 13C shows a step of removing the mask used for the formation of theindividual liquid chamber 13, and forming a mask for the communicationhole 12 and common liquid chamber 14, and FIG. 13D shows a step ofprocessing the communication hole 12 and common liquid chamber 14 byetching and the like from a lower portion. Moreover, FIG. 13Eschematically shows a state of removing the mask used for the formationof the communication hole 12 and common liquid chamber 14 to form theindividual liquid chamber 13, communication hole 12, and common liquidchamber 14. The discharge port 11 is formed by giving etchingprocessing, machining, laser processing, or the like to the substrate17. FIG. 13F shows a state that the substrate 17 in which the dischargeport 11 is formed is bonded to the substrate, in which the individualliquid chamber 13, communication hole 12, and common liquid chamber 14are formed, after step 13E. It is preferable that a surface of thesubstrate 17 in which the discharge port is provided is water-repellent.Although a bonding method of respective substrates is the same as thebonding method at the time of transfer, anodic oxidation bonding may bealso used.

In the second method, it is preferable to use another substrate, towhich the piezoelectric element 10 on the substrate 5 is transferred, ina state as shown in FIG. 13E or 13F. Here, when the vibrating plate isformed on the piezoelectric thin-film element on the substrate 5, it isdirectly transferred on the individual liquid chamber 13 in the stateshown in FIGS. 13E or 13F. In addition, when the vibrating plate is notformed on the piezoelectric element on the substrate 5, a hole of theindividual liquid chamber 13 in the state shown in FIGS. 13E or 13F isfilled up with a resin for the vibrating plate to be formed as a film,and it is transferred after this resin being removed by etching and thevibrating plate is formed. At this time, it is preferable to form thevibrating plate using a thin film forming method such as the sputteringmethod or CVD method. In addition, the pattern forming step of thepiezoelectric element 10 may be either before or after the transfer.

Next, a liquid discharge apparatus of this embodiment will be explained.The liquid discharge apparatus of this embodiment has theabove-mentioned liquid discharge head of this embodiment.

As an example of the liquid discharge apparatus of this embodiment, itis possible to mention an ink jet recording apparatus shown in FIGS. 14and 15. FIG. 15 shows a state that the exterior components 82 to 85, and87 of the liquid discharge apparatus (ink jet recording apparatus) 81shown in FIG. 14 are removed. The ink jet recording apparatus 81 has anautomatic feeding portion 97 which performs automatic feeding ofrecording paper as a recording medium into an apparatus main body 96.Further, it has a transport portion 99 which introduces the recordingpaper sent from the automatic feeding portion 97 to a predeterminedrecording position, and introduces the recording paper from therecording position to a sheet discharging port 98, a recording portion91 which performs recording on the recording paper transported in therecording position, and a recovery portion 90 which performs recoveryprocessing to the recording portion 91. The recording portion 91 isequipped with a carriage 92 which includes the liquid discharge head ofthis embodiment, and is reciprocally conveyed on a rail.

In such an ink jet recording apparatus, the carriage 92 is conveyed onthe rail by an electric signal sent out from a computer, and when adrive voltage is applied to the electrodes which sandwich thepiezoelectric substance, the piezoelectric substance is displaced. Eachpiezoelectric chamber is pressurized through the vibrating plate 15 bythis displacement of the piezoelectric substance, and ink is dischargedfrom the discharge port 11 for printing to be performed.

The liquid discharge apparatus of this embodiment can discharge theliquid at high speed uniformly, and can achieve miniaturization of theapparatus.

Although being exemplified as a printer in the above-mentioned example,the liquid discharge apparatus of this embodiment can be used as anindustrial liquid discharge apparatus besides an ink jet recordingapparatus for a facsimile, a compound machine, a copier, or the like.

EXAMPLES

Hereafter, the piezoelectric body and the piezoelectric element of thisembodiment, the liquid discharge head using this, and its productionmethod will be explained with citing examples.

Example 1

Fabrication sequence of a piezoelectric substance and a piezoelectricelement of a first example is as follows.

On a La-doped SrTiO₃ {100} substrate which served as a lower electrode,a 3-μm film thickness of piezoelectric substance PZT was formed as afilm with holding a substrate temperature of 600° C. by the sputteringmethod. A material whose main component was PZT and whose target densitywas 88% was used as a target. The element ratio {Pb/(Zr+Ti)} Target ofPb, Zr, and Ti of a target was made 1.00, and {Zr/(Zr+Ti)} Target wasmade 0.65. Sputtering was performed on the following conditions.Sputtering gas: Ar/O₂=20/1, sputtering power: 1.3 W/cm², sputtering gaspressure: 0.5 Pa. Film formation was performed so as to obtain 3 μm offilm thickness by adjusting sputtering time with holding a substratetemperature at 600° C. According to a composition analysis (ICPcomposition analysis) by an inductively coupled plasma atomic emissionspectrometer, as for element ratios of Pb, Zr, and Ti of thepiezoelectric substance, Pb/(Zr+Ti) was 1.40 and Zr/(Zr+Ti) was 0.53. Inaddition, according to 2θ/θ measurement of X-ray diffraction, only areflection peak resulting from the {00L} plane (L=1, 2, 3 . . . , n: nis an integer) of the perovskite structure of PZT was detected. Whenpositive pole measurement of an asymmetric plane {202} was performed,reflection peaks appeared in fourfold symmetry. Consequently, it wasconfirmed that the piezoelectric substance was a single crystal PZT filmwith the perovskite type structure of <100> orientation. Similarly,according to reciprocal lattice mapping (FIG. 16) of {004} and {204} bythe X-ray diffraction, it was confirmed that lattice constants of thissingle crystal film were a=4.08 Å, c=4.16 Å, and β=89.6°, that it was amonoclinic, and that c/a=1.02. In FIG. 16, rlu stands for reciprocallattice units. In addition, as for reciprocal lattice points resultingfrom the {204} plane, peaks were divided up and down, and hence, it wasconfirmed that monoclinics had a relation of a twin crystal.Furthermore, a Curie temperature Tc of the piezoelectric substance was500° C. Further, by a 4 nm-thick Ti film and a 150 nm-thick Pt filmbeing formed by the sputtering method in this order on the piezoelectricsubstance as electrode films, a pair of electrodes was formed, and thepiezoelectric element of the first example was produced.

Example 2

Fabrication sequence of a piezoelectric substance and a piezoelectricelement of a second example is as follows.

Tetrabutoxyzirconium and tetra-i-propoxy titanium were melted in a watermixture of butanol and acetylacetone in conformity to a compositionratio of Zr/Ti which is a target. Liquid of lead raw material liquidbeing added so as to become excessive lead, after adding 1 mol % ofdibenzylmethylamine to a metallic raw material as a base catalyst, andheating and aging it at 50° C. for 12 hours was coated on a La-dopedSrTiO₃ {100} substrate, which served as a lower electrode, by a spincoating method. As the lead raw material, a solution of a mixture oflead acetate with butanol and i-propanol was used.

Spin coating was repeated after coating, and heating at 600° C. for 30minutes and at 400° C. for 30 minutes for a film to be formed until afilm thickness became 3 μm. Then, heating was performed at 700° C. for 1hour for the piezoelectric substance to be formed.

According to the ICP composition analysis, as for element ratios of Pb,Zr, and Ti of the piezoelectric substance, Pb/(Zr+Ti) was 1.50 andZr/(Zr+Ti) was 0.55. In addition, according to 2θ/θ measurement of theX-ray diffraction, only a reflection peak resulting from the {00L} plane(L=1, 2, 3 . . . , n: n is an integer) of the perovskite structure ofPZT was detected. When the positive pole measurement of an asymmetricplane {202} was performed, reflection peaks appeared in fourfoldsymmetry. Consequently, it was confirmed that the piezoelectricsubstance was a single crystal PZT film with the perovskite typestructure of <100> orientation. Similarly, according to the reciprocallattice mapping of {004} and {204} by the X-ray diffraction, it wasconfirmed that lattice constants of this single crystal film were a=4.08Å, c=4.11 Å, and β=89.6°, that it was a monoclinic, and that c/a=1.01.In addition, a Curie temperature Tc of the piezoelectric substance was410° C. Further, by a 4-nm-thick Ti film and a 150-nm-thick Pt filmbeing formed by the sputtering method in this order on the piezoelectricsubstance as electrode films, a pair of electrode films was formed, andthe piezoelectric element of the second example was produced.

Comparative Example 1

A piezoelectric substance and a piezoelectric element of a firstcomparative example were produced in the following procedure.

As a target, a material whose main component was PZT whose targetdensity was 98%, and in which the element ratio {Pb/(Zr+Ti)} Target ofPb, Zr, and Ti of a target was 1.40 and {Zr/(Zr+Ti)} Target was 0.55 wasused. The piezoelectric substance and piezoelectric element of the firstcomparative example were produced under the same conditions as those inthe first example except using the above-mentioned target. According tothe ICP composition analysis, as for element ratios of Pb, Zr, and Ti ofthe piezoelectric substance, Pb/(Zr+Ti) was 1.30 and Zr/(Zr+Ti) was0.55. In addition, according to the 2θ/θ measurement of the X-raydiffraction, only a reflection peak resulting from the {00L} plane (L=1,2, 3 . . . , n: n is an integer) of the perovskite structure of PZT wasdetected. When the positive pole measurement of an asymmetric plane{202} was performed, reflection peaks appeared in fourfold symmetry.Consequently, it was confirmed that the piezoelectric substance was asingle crystal PZT film with the perovskite type structure of <100>orientation. Similarly, according to the reciprocal lattice mapping of{004} and {204} by the X-ray diffraction, it was confirmed that latticeconstants of this single crystal film were a=4.07 Å, c=4.15 Å, andβ=90.0°, that it was a tetragonal, and that c/a=1.02. In addition, asfor reciprocal lattice points resulting from the {204} plane,differently from the first example, it was confirmed that a peak was notdivided up and down. In addition, a Curie temperature Tc of thepiezoelectric substance was 390° C.

Example 3

Fabrication sequence of a piezoelectric substance and a piezoelectricelement of a third example is as follows.

After performing hydrofluoric acid processing of a Si(100) substratesurface, a 100-nm-thick Y-doped ZrO₂ film was formed at a substratetemperature of 800° C. by the sputtering method, and then, a 60-nm-thickCeO₂ film was formed at a substrate temperature of 600° C. Both weresingle crystal films of <100> orientation. Further, a 100-nm-thickLaNiO₃ (LNO) film was formed on this at a substrate temperature of 300°C. as a lower electrode film by the sputtering method. Furthermore, a200-nm-thick SrRuO₃ (SRO) film was formed at a substrate temperature of600° C. on this LNO film, and the substrate which had a lower electrodefilm and the like was obtained. The electrode film and SRO film weresingle crystal films of <100> orientation.

The above-mentioned substrate was used instead of the La-doped SrTiO₃{100} substrate, and the following was used as a target. As a target, amaterial whose main component was PZT whose target density was 88%, andin which the element ratio {Pb/(Zr+Ti)} Target of Pb, Zr, and Ti of atarget was 1.00 and {Zr/(Zr+Ti)} Target was 0.75 was used. Thepiezoelectric substance and piezoelectric element of the third examplewere produced under the same conditions as those in the first exampleexcept using these. According to the ICP composition analysis, as forelement ratios of Pb, Zr, and Ti of the piezoelectric substance,Pb/(Zr+Ti) was 1.45 and Zr/(Zr+Ti) was 0.65. In addition, according tothe 2θ/θ measurement of the X-ray diffraction, only a reflection peakresulting from the {00L} plane (L=1, 2, 3 . . . , n: n is an integer) ofthe perovskite structure of PZT was detected. When the positive polemeasurement of an asymmetric plane {202} was performed, reflection peaksappeared in fourfold symmetry. Consequently, it was confirmed that thepiezoelectric substance was a single crystal PZT film with theperovskite type structure of <100> orientation. Similarly, according tothe reciprocal lattice mapping of {004} and {204} by the X-raydiffraction, it was confirmed that lattice constants of this singlecrystal film were a=4.09 Å, c=4.13 Å, and β=89.5°, that it was amonoclinic, and that c/a=1.01. In addition, as for reciprocal latticepoints resulting from the {204} plane, peaks were divided up and down,and hence, it was confirmed that monoclinics had relation of a twincrystal. In addition, a Curie temperature Tc of the piezoelectricsubstance was 520° C.

Example 4

Fabrication sequence of a piezoelectric substance and a piezoelectricelement of a fourth example is as follows.

After a 4-nm-thick TiO₂ film was formed on a Si substrate on which a100-nm thick SiO₂ layer which was a thermal oxidation film was formed, a100-nm-thick Pt film was formed by the sputtering method at a substratetemperature of 200° C. The Pt film was a <111> orientation film.Further, a 100-nm-thick LaNiO₃ (LNO) film was formed on this at asubstrate temperature of 300° C. as a lower electrode film by thesputtering method. Furthermore, a 200-nm-thick SrRuO₃ (SRO) film wasformed at a substrate temperature of 600° C. on this LNO film, and thesubstrate which had a lower electrode film and the like was obtained.The electrode film and SRO film were uniaxial crystal films of <100>orientation.

Next, the piezoelectric substance and piezoelectric element of thefourth example were produced under the same conditions as those in thethird example except using the above-mentioned substrate which had thelower electrode film and the like. According to the ICP compositionanalysis, as for element ratios of Pb, Zr, and Ti of the piezoelectricsubstance, Pb/(Zr+Ti) was 1.35 and Zr/(Zr+Ti) was 0.63. In addition,according to the 2θ/θ measurement of the X-ray diffraction, only areflection peak resulting from the {00L} plane (L=1, 2, 3 . . . , n: nis an integer) of the perovskite structure of PZT was detected. When thepositive pole measurement of an asymmetric plane {202} was performed,ring-like peaks appeared. Consequently, it was confirmed that thepiezoelectric substance was a uniaxial orientation PZT film with theperovskite type structure of <100> orientation. Similarly, according tothe reciprocal lattice mapping of {004} and {204} by the X-raydiffraction, it was confirmed that lattice constants of this uniaxialorientation film were a=4.08 Å, c=4.14 Å, and β=89.0°, that it was amonoclinic, and that c/a=1.01. In addition, a Curie temperature Tc ofthe piezoelectric substance was 520° C.

Comparative Example 2

A piezoelectric substance and a piezoelectric element of a secondcomparative example were produced in the following procedure.

As a target, a material whose main component was PZT whose targetdensity was 98%, and in which the element ratio {Pb/(Zr+Ti)} Target ofPb, Zr, and Ti of a target was 1.05 and {Zr/(Zr+Ti)} Target was 0.45 wasused. The piezoelectric substance and piezoelectric element of thesecond comparative example were produced under the same conditions asthose in the third example except using the above-mentioned target.According to the ICP composition analysis, as for element ratios of Pb,Zr, and Ti of the piezoelectric substance, Pb/(Zr+Ti) was 1.02 andZr/(Zr+Ti) was 0.45. In addition, according to the 2θ/θ measurement ofthe X-ray diffraction, only a reflection peak resulting from the {00L}plane (L=1, 2, 3 . . . , n: n is an integer) of the perovskite structureof PZT was detected. When the positive pole measurement of an asymmetricplane {202} was performed, reflection peaks appeared in fourfoldsymmetry. Consequently, it was confirmed that the piezoelectricsubstance was a single crystal PZT film with the perovskite typestructure of <100> orientation. Similarly, according to the reciprocallattice mapping of {004} and {204} by the X-ray diffraction, it wasconfirmed that lattice constants of this single crystal film were a=4.04Å, c=4.17 Å, and β=90°, that it was a tetragonal, and that c/a=1.03. Inaddition, a Curie temperature Tc of the piezoelectric substance was 410°C.

Comparison of measurement result of piezoelectric constant and leakagecurrent in above-described example

Table 1 shows measurement results of the piezoelectric constant and theleakage current of the piezoelectric elements of the first to fourthexamples, and the first and second comparative examples. Here, thepiezoelectric constant was evaluated by processing the upper electrodeinto φ100-μm pattern, and measuring the piezoelectric constant in a d33mode which measured minute displacement with a scanning probe microscopy(SPM) at the time of applying a voltage between the upper and lowerelectrodes. In addition, the leakage current was evaluated by processingthe upper electrode into φ100-μm pattern similarly to the piezoelectricconstant measurement and measuring a leakage current between the upperand lower electrodes at the time of applying a DC voltage of 100Vbetween the upper and lower electrodes.

TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 4example 1 example 2 Piezoelectric 350 300 330 320 300 180 Constant(ρC/N) (pC/N) Leakage 3.5 × 10⁻⁷ 1.2 × 10⁻⁷ 4.7 × 10⁻⁶ 3.5 × 10⁻⁶ 2.2 ×10⁻³ 6.5 × 10⁻⁶ Current (A/cm²)

As shown in Table 1, although the first and second examples have anequal or larger piezoelectric constant in comparison with the firstcomparative example, the leakage current is suppressed low. In addition,it is possible to confirm that the third and fourth examples have thelarge piezoelectric constant in comparison with the second comparativeexample, and the leakage current is also suppressed.

Example 5 and Comparative Example 3

Next, liquid discharge heads of a fifth example and a third comparativeexample were produced in the following procedures.

An SOI substrate on which a 500 nm-thick epitaxial Si film and a500-nm-thicken SiO₂ layer were formed was used. A piezoelectric elementwas produced under the similiar conditions as those in the third exampleor the comparative example 2. After patterning an actuator portion, avibrating plate and an individual liquid chamber were formed bydry-etching the Si substrate, which was a handle layer, by theinductively coupled plasma method (ICP method). Next, another Sisubstrate on which a common liquid chamber and a communication hole wereformed on this was bonded together. Further, by bonding a substrate, inwhich a discharge port was formed, to the above-mentioned Si substrateon which the common liquid chamber and communication hole were formed, aliquid discharge head where the vibrating plate was constructed of theSiO₂ layer, Si film, Y-doped ZrO₂ film, and CeO₂ film was produced. Theliquid discharge head whose piezoelectric element was produced similarlyto the third example was made a liquid discharge head of the fifthexample, and the liquid discharge head whose piezoelectric element wasproduced similarly to the second comparative example was made a liquiddischarge head of the third comparative example. A drive signal wasapplied to and drove these liquid discharge heads, a φ20-μm laser beamwas radiated on a center portion of the individual liquid chamber of theliquid discharge head from an upper electrode side, and a displacementamount of the liquid discharge head was evaluated by a laser Dopplerdisplacement system. Although the liquid discharge head of the fifthexample showed displacement with good followability also to 10⁸ times ofdrive signals, the liquid discharge head of the third comparativeexample not only had a small displacement amount, but also showedattenuation of displacement by 10⁵ times.

Example 6

In regard to the piezoelectric substance formed as a film, this example,where lead was decreased in the range of this embodiment in comparisonwith the first example, was available preferably. Explanation ofportions the same as those in the first example will be omitted.

On a La-doped SrTiO₃{100} substrate which served as a lower electrode, a3-μm film thickness of piezoelectric substance PZT was formed as a filmwith holding a substrate temperature of 600° C. by the sputteringmethod. A material whose main component was PZT whose target density was88% was used as a target. The element ratio {Pb/(Zr+Ti)}Target of thetarget was made 0.85, and {Zr/(Zr+Ti)} Target was made 0.85. Sputteringwas performed under the conditions of sputtering gas: Ar/O₂=20/1,sputtering power: 1.6 W/cm², and sputtering gas pressure: 0.1 Pa. Atthis time, when a 3-μm film was formed with holding a substratetemperature at 620° C., Pb/(Zr+Ti) was 1.10, and Zr/(Zr+Ti) was 0.75.The piezoelectric substance was a single crystal film with the PZTperovskite type structure of <100> orientation, its lattice constantswere a=4.09, c=4.12 Å, and β=89.0°, it was a monoclinic, and c/a=1.007held. In addition, temperature dependency of a dielectric constant ofthe piezoelectric substance was the maximum at 540° C., and a Curietemperature Tc was 540° C.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2005-241396, filed Aug. 23, 2005, which is hereby incorporated byreference herein in its entirety.

1. A piezoelectric substance, wherein a main component of thepiezoelectric substance is PZT which has a perovskite type structureexpressed as Pb(Zr_(x)Ti_(1-x))O₃, x expresses an element ratioZr/(Zr+Ti) of Zr and Ti, an element ratio Pb/(Zr+Ti) of Pb, Zr, and Tiof the piezoelectric substance is 1.05 or more, an element ratioZr/(Zr+Ti) of Zr and Ti is 0.5 to 0.8 inclusive, and the piezoelectricsubstance has at least a perovskite type structure of a monoclinicsystem.
 2. The piezoelectric substance according to claim 1, wherein aCurie temperature Tc of the piezoelectric substance and a Curietemperature Tc₀ in bulk at the element ratio of Zr and Ti of thepiezoelectric substance satisfy a relation of Tc>Tc₀+50° C.
 3. Thepiezoelectric substance according to claim 1, wherein a film thicknessof the piezoelectric substance is 1 to 10 μm inclusive.
 4. Thepiezoelectric substance according to claim 1, wherein lattice constantsa and c of the piezoelectric substance satisfy a relation of1.005<c/a<1.05.
 5. The piezoelectric substance according to claim 1,wherein the piezoelectric substance is a uniaxial crystal or a singlecrystal.
 6. The piezoelectric substance according to claim 5, whereinthe piezoelectric substance has <100> orientation.
 7. A piezoelectricelement which has a pair of electrodes and a piezoelectric substance,wherein a main component of the piezoelectric substance is PZT which hasa perovskite type structure expressed as Pb(Zr_(x)Ti_(1-x))O₃, xexpresses an element ratio Zr/(Zr+Ti) of Zr and Ti, an element ratioPb/(Zr+Ti) of Pb, Zr, and Ti of the piezoelectric substance is 1.05 ormore, an element ratio Zr/(Zr+Ti) of Zr and Ti is 0.5 to 0.8 inclusive,and the piezoelectric substance has at least a perovskite type structureof a monoclinic system.
 8. The piezoelectric element according to claim7, wherein at least one of the electrodes includes an electrode made ofoxide with perovskite type structure which has <100> orientation.
 9. Aliquid discharge head which has an individual liquid chambercommunicating with a discharge port, and a piezoelectric element whichis provided in correspondence with the individual liquid chamber, andwhich includes a piezoelectric substance having a pair of electrodes,and discharges liquid in the individual liquid chamber from thedischarge port, wherein a main component of the piezoelectric substanceis PZT which has a perovskite type structure expressed asPb(Zr_(x)Ti_(1-x))O₃, x expresses an element ratio Zr/(Zr+Ti) of Zr andTi, an element ratio Pb/(Zr+Ti) of Pb, Zr, and Ti of the piezoelectricsubstance is 1.05 or more, and an element ratio Zr/(Zr+Ti) of Zr and Tiis 0.5 to 0.8 inclusive, and the piezoelectric substance has at least aperovskite type structure of a monoclinic system.
 10. A liquid dischargeapparatus which has a liquid discharge head which discharges liquid,wherein a piezoelectric element which generates energy for dischargingliquid has a piezoelectric substance and a pair of electrodes, andwherein a main component of the piezoelectric substance is PZT which hasa perovskite type structure expressed as Pb(Zr_(x)Ti_(1-x))O₃, xexpresses an element ratio Zr/(Zr+Ti) of Zr and Ti, an element ratioPb/(Zr+Ti) of Pb, Zr, and Ti of the piezoelectric substance is 1.05 ormore, an element ratio Zr/(Zr+Ti) of Zr and Ti is 0.5 to 0.8 inclusive,and the piezoelectric substance has at least a perovskite type structureof a monoclinic system.